Wireshark · Wireshark-users: [Wireshark-users] ICMP packets with two pairs of source and destination ip addresses?

[nangergong <nangergong@xxxxxxxxx>]

HI, all,
    
     I used tshark to parse a pcap file with icmp packets, 
                  tshark -r icmp -T fields -e frame.number -e ip.src -e ip.dst
 
     and the results are something like this:

1    74.125.132.188    138.96.192.56
2    74.125.132.188    138.96.192.56
3    138.96.192.56,74.125.132.188    74.125.132.188,138.96.192.56
4    138.96.192.56,74.125.132.188    74.125.132.188,138.96.192.56
5    74.125.132.188    138.96.192.56
6    138.96.192.56,74.125.132.188    74.125.132.188,138.96.192.56
7    74.125.132.188    138.96.192.56
8    138.96.192.56,74.125.132.188    74.125.132.188,138.96.192.56
9    74.125.132.188    138.96.192.56
10    138.96.192.56,74.125.132.188    74.125.132.188,138.96.192.56
11    74.125.132.188    138.96.192.56
12    138.96.192.56,74.125.132.188    74.125.132.188,138.96.192.56


so , like 3, 4, 6,8,10,12 , there are two src ip addr and dst ip addr
what is the reason for this? thanks